The casting of metals has been practiced for more than 6000 years, using first copper, then bronze, and then iron. Die castings are produced by forcing molten metal under pressure into permanent steel dies. Die casting involves metal flow at high velocities induced by the application or pressure. Because of this high-velocity filling, die casting can produce shapes that are more complex than shapes that can be produced by permanent mold casting. In die casting, after the die has been closed and locked, molten metal is delivered to a piston pump, which may be cold or may be heated to the temperature of the molten metal. The pump plunger is advanced to drive the metal quickly through the feeding system while the air in the die escapes through vents. Sufficient metal is introduced to overflow the die cavities, fill overflow wells and develop some flash. As the extraneous metal solidifies, pressure is applied to the remaining metal and is maintained through a specified dwell time to allow the casting to solidify. The die opens and the casting is then ejected. While the casting die is open, it is cleaned, cooled and lubricated as required. Then the die closed and locked, and the cycle is repeated. In a cold-chamber system, molten metal is generally delivered from the bottom to a shot chamber and then filled into the casting cavity by means of the operation of a pump plunger which is disposed in a horizontal position. Because molten metal is filled into the casting cavity from the bottom, the lower part of the molten metal filled in the casting cavity will become solidified firstly. Therefore, it is very difficult to arrange a suitable pouring hole. Since the lower part may be solidified while molten metal is still pouring through the pouring hole, it is difficult to obtain a satisfactory homogeneous solid of the die casting, and a high pressure cylinder or booster equipment is difficult to install.